The FFmpeg version of Nvidia Codec SDK headers which are required
to interface with Nvidia's codec APIs. The purpose of these
headers is to allow hardware (GPU) encoding with suitable NVidia
cards. This version corresponds to Video Codec SDK version 11.1.5
and requires NVidia drivers version 470.57.02 or newer.

There are 3 stages in the history of NVidia GPU encoding with FFmpeg:

 1. Pre August 27th 2016 it was necessary to track down your own
    headers to build nvenc.
 2. Post August 27th 2016 the required headers were incorporated
    as part of the FFmpeg source.
 3. Post February 26th 2018 the NVidia headers were removed from
    the FFmpeg source and a separate git repository was created
    to hold continuing work with these headers.

This nv-codec-headers script is for point 3 where the headers will
need to be installed before compiling a recent FFmpeg.
